Fuel Injection Distribution Control; Synchronized Injection Control - Mazda RX-8 2004 Service Highlights

Fuel Injection Distribution Control

• There are primary 1, secondary and primary 2 (13B-MSP (High Power)) injectors, and they independently
control fuel injection amount and timing according to the amount of fuel demand from the engine.
• The amount of fuel demand from the engine is determined by each correction of the charging efficiency and
injection time after engine start.
• When the amount of fuel demand from the engine
is low, only the primary 1 injectors inject fuel.
When the amount of fuel demand from the engine
increases, fuel injection in the order of secondary
injector and primary 2 injector (13B-MSP (High
Power)) begin injection.

Synchronized Injection Control

• The synchronized injection control performs fuel injection according to each timing that has been determined
by the intake stroke of the rotors.
• The synchronized injection control includes fuel injection control at engine start and fuel injection control after
engine start. Synchronized injection control performs fuel injection based on injection time (final injection pulse
width) and fuel injection timing demanded by each rotor.
Injection time at start
• Calculated by adding the engine speed correction to the basic injection time at engine start, the throttle valve
opening angle correction, the BARO correction, and the volume decrease correction at engine start, and then
the final injection pulse width is calculated by adding the ineffective injection time to the injection time at engine
start.
• Basic injection time at engine start is determined based on ECT and shortens as the ECT increases.
• Ineffective injection time is determined according to battery voltage and lengthens as battery voltage becomes
lower.
Correction
Engine speed correction
Throttle valve opening angle
correction
BARO correction
Volume decrease correction
at engine start
Injection time after engine start
• The injection time after engine start is calculated from the charging efficiency, ineffective injection time and
each type of correction.
Charging efficiency
— The charging efficiency is the ratio of intake air amount that is actually taken in relation to the maximum air
charging amount (mass) of the operation chamber. This value becomes larger in proportion to the increase
in engine load.
CONTROL SYSTEM
Condition
Determines correction amount based on
engine speed.
Determines correction amount based on
throttle valve opening angle.
Determines correction amount based on BARO
sensor.
Determines correction amount based on ECT
and engine speed at engine start.
SECONDARY INJECTOR
PRIMARY1 INJECTOR
PRIMARY2 INJECTOR
ENGINE DEMAND
LOW
FUEL VOLUME
Amount of Correction
• Correction amount lengthens as the engine
speed increases.
• Correction amount shortens as the throttle
valve opening angle increases.
• Correction amount lengthens (time) as the
BARO increases.
• After starter is on for approx. 1 s and any
one of the following conditions are met,
injection time gradually decreases:
— ECT at fixed value or more
— Engine speed at target engine speed or
more
— Approx. 5 s of cranking time elapsed
01–40
HIGH
CHU0140S019
01–40–21